Prior art flushometers have included a two part diaphragm-disc assembly. The diaphragm plate was typically a rubber component with a metallic core (for support). The diaphragm serves to control the main (primary) water flow through a flushometer by the use of a bypass. The relief valve seat was a separate component that engaged with the diaphragm. In prior art devices, the relief valve seat typically was an additional part also rubber molded around a metallic base.
As lower flush volume fixtures have become necessary and popular, there is a need for flushometers to deliver tighter variability to each flush delivered. This requires tighter control over the components which in-turn give tighter control over the flush profile (both total volume per flush and volume per time.)